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BackgroundRefugia are island-like habitats that are linked to long-term environmental stability and, as a result, high endemism. Conservation of refugia and endemism hotspots should be based on a deep ecological and evolutionary understanding of their functioning, which remains limited. Although functional traits can provide such insights, a corresponding, coherent framework is lacking.Proposed frameworkPlant communities in refugia and endemism hotspots should, due to long-term environmental stability, display unique functional characteristics linked to distinct phylogenetic patterns. Therefore, such communities should be characterized by a functional signature that exhibits: (1) distinct values and combinations of traits, (2) higher functional diversity and (3) a prevalence of similar traits belonging to more distantly related lineages inside, compared to outside, of endemism hotspots and refugia. While the limited functional trait data available from refugia and endemism hotspots do not allow these predictions to be tested rigorously, three potential applications of the functional signature in biogeography and conservation planning are highlighted. Firstly, it allows the functional characteristics of endemism hotspots and refugia to be identified. Secondly, the strength of the functional signature can be compared among these entities, and with the surrounding landscape, to provide an estimate of the capacity of endemism hotspots and refugia to buffer environmental changes. Finally, the pattern of the functional signature can reveal ecological and evolutionary processes driving community assembly and functioning, which can assist in predicting the effect of environmental changes (e.g. climate, land-use) on communities in endemism hotspots and refugia.ConclusionThe proposed functional signature concept allows the systematic integration of plant functional traits and phylogeny into the study of endemism hotspots and refugia, but more data on functional traits in these entities are urgently needed. Overcoming this limitation would facilitate rigorous testing of the proposed predictions for the functional signature, advancing the eco-evolutionary understanding of endemism hotspots and refugia.

Bioregionalisation partitions diversity so that similarity of the selected biological and ecological variables is higher within regions than it is outside those regions. The classic approach partitions an area based on species composition, whereas more recent methods based on remotely sensed data classify biogeographic regions on biophysical and structural variables of vegetation. Another, yet to be explored opportunity, is offered by identifying distinct ecological strategies of plants inhabiting a given area, that is, a functional trait‐based bioregionalisation. Here, we propose such a bioregionalisation using trait hypervolumes. We also compare the proposed functional bioregionalisation with established classifications based on species composition or on remotely sensed data to identify spatial congruence among them, and suggest possible reasons behind observed patterns.Natural history collections represent an underexploited resource, despite holding both trait and locality information and being taxonomically comprehensive. We compile values of traits (leaf size, plant height, seed number per fruit, seed volume) derived from natural history collections for a random sample of African angiosperm species (~1% of the continental flora) to estimate a trait hypervolume. We use hierarchical clustering to divide the hypervolume into four segments (each representing a distinct ecological strategy), whose spatial intersections produced 12 putative biogeographic regions, each containing one or more of these strategies. We spatially map the hypervolume segments onto the entire African continent and calculate the spatial congruence of the putative functional biogeographic regions with previous bioregionalisations.We identify values and combinations of traits that can be indicative of biogeographic regions. This functional bioregionalisation shows greater spatial congruence with that derived from species composition than from remote sensing. However, spatial congruence is low at the continent scale (19%–37%), and varies greatly among regions and in pairwise comparisons between bioregionalisations.Synthesis. Plant traits from natural history collections offer an underused source of information for biogeographic analyses. We demonstrate potential applications of trait hypervolumes in functional biogeography, and outline strengths and drawbacks of the different bioregionalisation methods. Finally, we suggest that key ecological strategies could be used in future models as proxies to anticipate shifts of species assemblages and biogeographic regions. [ABSTRACT FROM AUTHOR]

Evolutionary history and environmental filtering shape the phylogenetic and functional structure of regional assemblages. However, detecting the footprint of such eco‐evolutionary drivers is challenging because these may often counter each other's signature. Here, we examined whether a biogeographic deconstruction approach of phylogenetic (PD) and functional diversity (FD) patterns may help in identifying eco‐evolutionary signals in extant regional assemblages. As model system, we used forest understorey angiosperms found in three regions of Italy (Alpine, Mediterranean, Continental). We quantified PD and FD of all species inhabiting the three regions (regional assemblages). Then, we computed PD and FD for the subsets of species restricted to each region (biogeographic elements), also examining diversity patterns of species found across the three regions (widespread element). We used aboveground and belowground traits capturing major plant functions to calculate FD. Additionally, we assessed FD patterns decoupled from phylogeny. We found that species restricted to climatically harsh regions (Alpine and Mediterranean elements) were phylogenetically and functionally clustered, whereas widespread species were characterised by overdispersion. Species confined to the climatically intermediate (Continental) region were randomly sorted. By including all species occurring within a region, the patterns found for the region‐restricted species blurred. Phylogenetically decoupled FD patterns were qualitatively similar to non‐decoupled ones with the exception of the Alpine element, where we detected a clear signature of functional differentiation between closely related species. This suggests that recent speciation events contributed to shaping the Alpine flora. Compared to the belowground compartment, aboveground traits showed a more coherent pattern with that of all‐trait FD – likely because most biomass is allocated aboveground in forest understoreys. This biogeographic deconstruction study illustrates which type of eco‐evolutionary insights can be gained by implementing multifaceted and integrated approaches at the macroecological scale. [ABSTRACT FROM AUTHOR]

Southwestern Australia (SWA) is a global biodiversity hotspot characterized by a mediterranean climate and is among the world's oldest and resource-poorest landscapes. Within this region, granite outcrops provide habitat complexity, and contribute to high levels of species diversity and endemism. Granite outcrop plant species are characterized by distinct anatomical, morphological and eco-physiological traits. So far, functional studies of SWA granite outcrop plants examined trait patterns along the stark aridity gradient that occurs in the region. Despite precipitation seasonality being an important climatic driver of plant species richness and distribution in mediterranean-type ecosystems, relationships between plant traits and precipitation seasonality remain understudied. Here, we investigated granite outcrop species' responses to changes in precipitation seasonality in terms of average and variability values of leaf traits related to water use efficiency. We found that plants displayed more acquisitive and variable trait values with increasing precipitation seasonality. These patterns are likely associated with the long-term effect of the stable and predictable precipitation regime in the old SWA that may have fine-tuned plant water use strategies to maximize water acquisition during the most favourable season. [ABSTRACT FROM AUTHOR]

Refugia are key environments in biogeography and conservation. Because of their unique eco‐evolutionary formation and functioning, they should display distinct functional trait signatures. However, comparative trait‐based studies of plants in refugia and non‐refugia are lacking. Here, we provide a comparison between resource‐rich (putative microrefugia for species preferring mesic habitats under increasing aridity) and resource‐impoverished woodlands (non‐refugia) around two granite outcrops in south‐western Australia. We measured and compared six functional traits (bark thickness, foliar δ13C, foliar C:N, leaf dry matter content, plant height, specific leaf area) in four woody species. We performed multiple‐trait, multiple‐species and single‐trait, within‐species analyses to test whether plants in resource‐rich habitats were functionally distinct and more diverse than those in the surrounding resource‐impoverished woodlands. We found that species in resource‐rich woodlands occupied larger and distinct multiple‐trait functional spaces and showed distinct single‐trait values (for specific leaf area and bark thickness). This suggests that plants in resource‐rich woodlands can deploy unique and more diverse ecological strategies, potentially making these putative microrefugia more resilient to environmental changes. These findings suggest that species in microrefugia may be characterised by unique functional signatures, illustrating the utility of comparative trait‐based approaches to improve understanding of the functioning of refugia. [ABSTRACT FROM AUTHOR]